Background: Currently, clinical trials for new therapeutic strategies are being planned for Duchenne and Becker muscular dystrophies (DMD/BMD). However, it is difficult to obtain adequate numbers of patients in clinical trials. As solutions to these problems, patient registries are an important resource worldwide, especially in rare diseases such as DMD/BMD. Methods: We developed a national registry of Japanese DMD/BMD patients in collaboration with TREAT-NMD. The registry includes male Japanese DMD/BMD patients whose genetic status has been confirmed by genetic analysis. The registry includes patients throughout Japan. Results: As of February 2012, 583 DMD and 105 BMD patients were registered. Most individuals aged less than 20 years. In terms of genetic mutations of registrants of DMD and BMD, deletion of exons was the most frequent (61.4% and 79.0%) followed by point mutations (24.5% and 14.3%) and duplications (13.6% and 4.8%), respectively. 43.6% of DMD are capable of walking, and 76.2% of BMD registrants are able to walk. 41.1% of DMD registrants in the database were treated using steroids. 29.5% of DMD and 23.8% of BMD registrants were prescribed one cardiac medicine at least. 22% of DMD used ventilator support, and non-invasive support was common. Small numbers of DMD and BMD registrants, only 3.9% and 1.0% of them, have received scoliosis surgery. 57 (9.8%) patients were eligible to clinical trial focused on ‘skipping’ exon 51. Conclusions: The Remudy has already demonstrated utility in clinical researches and standardization of patients care for DMD/BMD. This new DMD/BMD patient registry facilitates the synchronization of clinical drug development in Japan with that in other countries.